Electronic organ reiteration system utilizing a zero-crossing preference circuit



Nov. 4. 1969 w. MUNCH, JR. ET AL 3,476,864

ELECTRONIC ORGAN REITERATION SYSTEM UTILIZING A ZERO-CROSSING PREFERENCE cmcum Filed March 9, 1966 5 Sheets-Sheet 1 IFI'GJ.

I5 (I7 20 2|) 22 I Z IASB'RE GATE v \AMPLIFIER FILTER Hi] II {@41 3 I I0 '9 26 2? (gittwl Eo T g u W SWITCH bdzs -k/ CLIPPING GATE AMPLIFIER A -I6 Is V I70 200 2lu 2 S S CLIPPING 29 6ATE LAMP FILTER AMP IFIER DIVIDER r m: r 20b r 2!!) CHAIN GATE 1 AMP FILTER I GATE AMP FILTER zoc 3 '0 23 I9 2Ic T I SINGLE 22 -\o-WlPE0UT x SWITCH NOTE 05C. rbg BLOCK 1 I I '2 M a! GATE|8ID DIVIDER GATE INVENTORS CLIPPING CHAIN l8 WALTER MUNCH, Jr. AMPLIFIER f c aoALE M. UETRECHT GATE Q I BY 7AM; XX I W zmm United States Patent US. Cl. 841.03 13 Claims ABSTRACT OF THE DISCLOSURE A system for sounding in reiterative alternation the highest and the lowest notes called for in playing a chord containing two or more notes.

The present invention relates generally to electric organs and more particularly to reiteration circuits for electric organs. 7

It is well known in the electric organ art to cause a tone to be sounded reiteratively so long as the playing key remains activated which called forth that tone. The capability of sounding tones reiteratively is of value in simulating banjo or mandolin music, and this can be accomplished by the unskilled player when the reiteration facility is available.

Heretofore, reiteration has been accomplished in response to a single tone only, or, if a chord is sounded, all the tones of the chord are reiterated together. In accordance with the present invention a novel reiteration capability is provided. If a chord is played, the highest and the lowest tone of the chord are called forth persussively in alternation reiteratively, while the remainder of the chord remains silent, regardless of the number of tones in the chord. But, if a single key is depressed, that note is called forth reiteratively, in distinctly spaced, rapidly repeated percussive pulses of tone.

This application is related to Walter Munch, Jr. application Ser. No. 466,170, filed June 23, 1965, now Patent No. 3,417,188 and entitled Preference Circuit. The latter application teaches circuitry for selecting either the highest note or the lowest note of a chord, to the exclusion of the remaining notes of the chord. The system of that invention includes a resistive network, having series and shunt elements arranged in the form of a cascaded array of resistive T or 1r networks, the tone sources being applied to the shunt elements. If the tone sources are connected to the shunt elements in ascending order of pitch, the lowest tone alone can be derived from one end of the array and the highest tone alone from the other end of the array. This capability is availed of, in the present invention, by applying a chord to a preference circuit, of the type disclosed in Ser. No. 466,170, now Patent No. 3,417,188 and selecting two of its tones for application to an alternating reiteration circuit. The two tones selected by the preference network are then sounded in alternation, so long as the chord is called forth.

The general arrangement of the system is, to apply the tones to be alternated to two normally non-conductive gates, which are rendered conductive in alternation. However, the tones can be used to control a frequency divider chain so that tones of different footages may be individually or simultaneously called forth by depression of one key.

It is, accordingly, a broad object of the invention to provide a reiteration circuit capable of calling forth two notes in alternation.

It is another object of the invention to sound the high- Patented Nov. 4, 1969 est and lowest notes of a chord in alternation, when the chord is called for by key depression.

It is a further object of the invention to combine a preference circuit with a reiteration circuit.

A problem arises, where one note is called forth in a glven organ in that the alternating reiteration of this one note would form an apparent doubling of the rate. According to a feature of the present invention, when two identical notes are present reiteratively, in alternation, one of these notes is automatically silenced so that only one note sounds reiteratively.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a block diagram of a simplified version of the present invention;

FIGURE 2 is a block diagram of a complete version of the present invention; and

FIGURES 3 and 3a are a schematic circuit diagram of the system of FIGURE 2.

In FIGURE 1, 10 is a wipeout switch which provides a first tone on its output lead 11, and a second tone on its output lead 12. The switch 10 combines all tones called forth by closure of plural ones of switches 13 from oscillators or tone sources 14, but the highest frequency called forth appears at greater amplitudes at lead 11, and the lowest frequency at lead 12.

The wave forms available on leads 11 and 12 are clipped by clipping amplifiers 15, 16, each of which selects that portion of the total wave shapes, i.e., the zero crossings, which correspond with one tone, in this case amplifier 15 selecting the highest frequency and amplifier 16 the lowest frequency. The wipeout switch 10 and the clipping circuits 15, 16 together constitute a preference network and by arranging oscillators 14 in order of increasing pitch, the highest and lowest pitches may be selected. The highest pitch is applied to gate 17 and the lowest pitch to gate 18. A multivibrator oscillator 19 applies gating waves to the gates 17, 18 in alternation, so that one of gates 17, 18 is conductive at any one time, and the other gate is then non-conductive. The total outputs of gates 17, 18 is applied to amplifier 20. The output of the latter is passed through a tone forming filter 21 and radiated acoustically by a loudspeaker 22.

The gates 17, 18 may be wave shaping gates, i.e., may provide a smooth but rapid rise and a sustained or slow decay, as indicated by the waveforms at 25. Specifically, the total tone which is acoustically radiated consists of alternate tones 26, 27, which have been shaped and formed to conform with the tonal wave shapes produced by the instrument, as mandolin or banjo, which it is desired to simulate.

FIGURE 2 is a modification of the system of FIGURE 1, which contains two improvements over FIGURE 1. Specifically, the outputs of clipping amplifiers 15, 16 are applied to frequency divider chains, 30, 31, providing two stages of division. From each stage is derived a tone, and the tones are individually selected by gates 17a, 17b, 17c. Similarly, clipper amplifier 16 drives divider chain 31, duplicating chain 30, and the three outputs of chain 31 are individually selected by gates 18a, 18b, 18c. The outputs of gates 17a, 18a are collected by amplifier 20a; the outputs of gates 18b by amplifier 20b; and the outputs of gates 17c, by amplifier 200. The outputs of the amplifiers 20a, 20b, 200 are separately filtered by tone color filters 21a, 21b, 21c and radiated acoustically by loudspeaker 22.

Single note block 23 accepts signals from clipping amplifiers 15 and 16 and compares these. If they are the same, control signal from reiteration oscillator 19 is blocked in its path to gates 17a, 17b, and 17c, but otherwise is not blocked. Thereby, when a single note is played it is not alternated with itself.

FIGURE 3 represents a schematic circuit diagram of the system of FIGURE 2, with minor modifications. In FIGURE 3A, 14a14d, inclusive, are tone sources, i.e., oscillators or components of frequency dividers. These are connected at will, via key switches 13a.13d, inclusive, and output impedances 30a, 30b, 30c, 30d to junction points 31, 32, 33, 34 of a string of resistances. The components described to this point are called a wipeout switch, which has two output leads 35, 36.

It can then be shown that each of generators 14a-14d proceeds to output lead 35 via a different series impedance, and to output lead 36 via a different series impedance. If plural switches 13a-13d are simultaneously closed, plural tones will proceed simultaneously to leads 35 and 36 but that generator nearest to lead 35 will provide signal at lead 35 at highest amplitude and that generator nearest to lead 36 will provide signal at lead 36 at highest ampli' tude. For example, if all of switches 13a-13d are closed simultaneously, generator 14a will provide maximum signal to lead 36 and generator 14d to lead 35, and generators 14b, 14c will be subordinated in amplitude at both leads 35, 36.

Assume that generators 14a-14d are arranged in order of pitch 'or frequency and are of square wave form. It then follows that zero crossings will occur at the frequency of generator 14a, on lead 36 and at the frequency of generator 14d on lead 35. The reasoning behind the conclusion is expanded in Ser. No. 466,170, now Patent No. 3,417,188 above referred to.

Lead 35 proceeds to clipping amplifier 40 of FIGURE 3, and lead 36 to clipping'amplifier 41.

Considering clipping amplifier 40 as exemplary, transistor T; has its collector connected to +115 v. via resistance 42 of 100K, and its emitter connected to ground via a small resistance 43, of 6800. This emitter is also connected to a bias voltage of 4.5 v. via resistance 44 of 2.7K. It follows that the emitter of T is at a potential slightly below ground, such that the on-condition of the transistor occurs when the base is approximately zero. The base of T is connected to --4.5 v. via a very large resistance 45 of M. The square waves provided by generators 14a14d are 8 v. peak to peak with no D.C. component. Transistor T is thus arranged to cut-off on a slight negatively going voltage and to saturate on a slight positively going voltage, with respect to ground. Thereby, transitions of voltage occur at the base of T only during zero-crossings of the signal voltages.

Transistor T is an amplifier clipper, which amplifies its input signal, but saturates to provide square waves, and transistor T operates solely as an amplifier. The emitter resistance 43a of 2209 provides clipped signal to lead 46, which is required for control of a single note block 46a, hereinafter explained in detail, while transistor T supplies its output to a gate 47. The gate 47 includes a series capacitor C a series diode D and a series resistance R (120K.). The input terminal of the gate is A. A point B is located between capacitor C and the cathode of diode D and. the output terminal is C. A shunt diode D; has its anode connected to point B and its cathode connected via a resistance R to a gating voltage input terminal D. The gating voltage terminal D is connected via lead 50 to the collector of a transistor T FIGURE 3A, which acts as a switch, being driven by voltage supplied by one side of a conventional multivibrator oscillator 51 from a condition in which lead 50 is well isolated from ground to a condition in which lead 50 is grounded.

Assume that lead 50 is grounded by transistor T and that signal is applied to point A. Point B is prevented from going positive by diode D and therefore the signal can only swing negative at point B. This negative voltage is passed by diode D and resistance R to output terminal C. Point D is then isolated from ground by transistor T whereupon the DC potential at point B begins to shift in the positive direction due to unidirectional flow of current through D which charges the capacitor C Thereby, the signal passed by the gate decays. The rate at which the signal decays away is determined .by the time constant of C R The rate at which signal builds up is determined by C R If transistor T grounds point D at some time thereafter, when no signal is then flowing, no undesirable signal occurs at point C due to the switching action.

For the sake of example, oscillator 51 may have a frequency of 7 c.p.s., and it applies its voltage as a positive square pulse of about sec. duration, followed by a space of the same duration, via capacitor 52 and resistance 53 to the base of transistor T The capacitor 52 and resistance 53 act to differentiate the square pulse, generating an extremely short positive pulse, followed after 4 sec. by an equally short negative pulse. The latter is removed by diode D Accordingly, two time constants exist, one when T grounds point D and the signal builds up as negatively going pulses, by loss of positive charge from the B side of C via D R The other is the charge time of C R until the B side of C becomes charged to the level of the signal peaks and cuts off D The net shape of the gen erated tone pulses is that illustrated in FIGURE 1 implying that the two time constants are not equal.

The signal supplied by transistor T drives a two-stage frequency divider, composed of divide-by-two flip-flops 60 and 61, which are per se conventional in character. The direct tone provided by T is then considered a 2' tone, while the outputs of flip-flops 60 and 51 are, respectively, 4' and 8' tones.

Each flip-flop is provided with its own gate, driven from T identical in character to the 2' gate, but not necessarily having the same time constants. For example, capacitors 65, 66 in the 4' and 8' gates are of .1 microfarad and .18 microfarad whereas C to which these correspond in function, is .0068 microfarad. Other components have the same values in all gates. The result is that the 2' tone component has short time constant of rise and decay and is used as a strike component for the other voices.

In FIGURE 3, a single amplifier 70, conventional per se, is used to sum the outputs of the 2' and 4' gates, and to pass these to a tone color filter 71. The 8 gate is provided with a separate amplifier 72 and tone color filter 73. Separate stop switches 74a, 74b are supplied for tone color filters 71 and 73. The 2' and 4' voices can only be heard together, and the 8' voice can be heard alone or with the 2' and 4' voices. However, as illustrated in the block diagram of FIGURE 2, the 2' and 4 voices can be obtained independently, if desired.

The lead 36 like the lead 35, proceeds to clipping amplifier 41, which includes a zero crossing detector 75, a clipping amplifier 76, and an amplifier 77. These generally follow the design of clipping amplifier 40', except in that T has an emitter load which supplies signal to lead 46, and the transistor T of stage 76 does not, but instead has a small resistance 79 in series between positive supply lead 80 and the collector load 81 of transistor T Resistance 79 supplies a signal to lead 85 which is equal to, but out of phase with the signal on lead 46 because of its location in a collector circuit, whereas lead 46 takes its signal from an emitter. Both signals are applied to the base of T where they cancel out and produce no effect. If they do not cancel out a net signal is applied to the base of T This signal is rectified by D and D providing a negative signal on capacitor C which opens circuits transistor T permitting T to operate. If T is not open circuited, it provides a short circuit around the base to emitter circuit of T preventing its operation.

The function of T is analogous to the function of T so that if it cannot operate, the 2', 4' and 8' gates associated with clipping amplifier 41, and the flip-flops 60a and 61a driven therefrom do not become conductive.

The 2 and 4 gates driven by clipping amplifier 41 and flip-flop 60a are connected via leads 92, 93 to a junction 94, which is in turn connected to the input of amplifier 70 via lead 94a. Similarly the 8 gate driven from flip-flop 61a is connected to the input of amplifier 72 via lead 98.

In summary, the wipeout switch may have only one of its key switches 13a-13d depressed or closed. If so, two synchronous wave shapes of opposite phase are applied to the base of T of single note block 46a. The transistor T then disables transistor T and only one set of tones is heard, i.e., those deriving from clipping amplifier 40, and flip-flops 60, 61.

It two of switches 13a-13d are depressed or closed, the upper tone alone proceeds to clipping amplifier 4Q; and the lower tone alone proceedsto clipping amplifier 41. Transistor T is open circuited, and T enabled. Oscillator 51 then supplies gating signals in alternation to, gate 47 and its associated 4' and 8 gates to cause the selected two notes to sound in alternation and reiteratively. Oscillator 51 may be activated, i.e., started, in response to the playing of a key by supplying signal deriving from clipping amplifier 41 to the oscillator via lead 95. ,This signal is rectified by diodes D and D providing a positive voltage on capacitor C which renders transistor T conductive. The consequent grounding of the emitter of transistor T is sufficient to start the oscillations, with rate control provided by adjustment of voltage on the slider of 100K pot 97. It will be understood, of course, that other methods of starting oscillator 51 may be employed, if desired.

If more than two of switches 13a-13d are actuated, only the highest and lowest of the notes called forth will in fact sound, and the intermediate notes are suppresse at the clipping amplifiers 40 and 41.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In an electric organ,

(a) a tone generator providing a gamut of organ key responsive tone signals according to a musical scale, each called forth by a different one of said keys,-

(b) means responsive to any plurality of said tone signals called forth simultaneously for sounding in alternation and reiteratively only the highest and the lowest of the plurality of tones called for by said tone signals.

2. The combination according to claim 1 wherein said plurality of tones is two.

3. The combination according to claim 1 wherein said plurality of tones is greater than two.

4. The combination according to claim 3 wherein said last means includes a preference circuit for transferring said highest and lowest of said plurality of notes to separate leads.

5. The combination according to claim 1 wherein said means includes a pair of gates responsive individually to said highest and lowest of said plurality of tones, and

means rendering said gates transmissible in alternation and reiteratively.

6. The combination according to claim 4 wherein is further provided a separate gate in cascade with each of said leads, and

means rendering said gates conductive in alternation and reiteratively.

7. The combination according to claim 6 wherein is further provided means responsive automatically to playing one only of said keys for playing said one note reiteratively in a predetermined time spaced relation.

8. The combination according to claim 5 wherein said means rendering said gates conductive includes a reiteration oscillator for rendering said pair of gates conductive and non-conductive in alternating sequence, and

means for summing the outputs of said pair of gates to pass said tones in alternation and reiteratively.

9. The combination according to claim 1 wherein said means includes a pair of gates responsive individually to said highest and lowest of said plurality of tones,

means further responsive individually to said highest and lowest of said plurality of tones for dividing the frequencies thereof,

a plurality of gates responsive individually to each of the frequency divided tones emanating from said frequency dividing means, and

means rendering all of the gates associated with the highest of said tones and the frequency divisions thereof and all of the gates associated with the lowest of said tones and the frequency divisions thereof respectively conductive in alternation and reiteratively.

10. The combination according to claim 9 wherein said means rendering said gates conductive includes a bistable multivibrator for supplying trigger voltages in alternation to said gates, and

wherein is further included means for summing the outputs of said pair of gates and for respectively summing the outputs of gates associated with corresponding frequency divisions of said highest and lowest tones.

11. In an electric organ,

a tone generator providing a plurality of key responsive tones according to a musical scale,

means comprising a preference network responsive to sustained depression of two of said keys for calling forth reiteratively and in alternation the tones corresponding with said two of said keys, and

means responsive to release of one of said keys for removing the tone corresponding with that one of said keys without changing the timing of the tone called forth by the other of said keys.

12. In an electronic organ,

a gamut of organ keys corresponding with a musical scale,

preference means responsive to actuation of any plurality of at least three of said keys corresponding with a chord for calling forth only two notes of said chord in alternation, one of said notes being the highest note of said chord and the other of said notes being the lowest note of said chord.

13. The combination according to claim 12, wherein said preference means is a circuit response to a plurality of discrete tone signals simultaneously for selecting on separate leads the highest frequency and lowest frequency only of said tone signals.

References Cited UNITED STATES PATENTS 2,685,039 3/1952 Scarbrough et al 307-259 3,378,624 6/1964 Markowitz 841.25

HERMAN KARL SAALBACH, Primary Examiner F. PRINCE BUTLER, Assistant Examiner U.S. Cl. X.R. 841.24 

